1. Field of the Invention
This invention relates to apparatus for replacing or installing components mounted on printed circuit boards (PCB's) and the like and, in particular, to apparatus for replacing or installing components mounted on such boards utilizing through-hole mountings.
Surface mounted devices (SMD's) have come into use in the last ten years or so, such devices being mounted on the same side of a printed circuit board the printed circuit is present. However, 85 to 95 percent of the electronic devices currently used in PCB assemblies utilize through-hole mounting--that is, the device is mounted on one side of the board and the leads therefor extend through plated-through holes or the like extending through the board to termination pads for the printed circuit on the opposite of the board. Apparatus for removing such devices are known such as those disclosed in U.S. Pat. Nos. 3,557,430 and 4,412,641. These devices have various shortcomings in terms of cost, maintenance, and/or use which are resolved by the component replacement device of the present invention. Other prior art of interest is U.S. Pat. Nos. 3,684,151; 3,731,866; 4,022,370; and 4,162,034.
2. Summary of the Invention
Accordingly, it is a primary object of the present invention to provide an improved component removing apparatus where the components are through-hole mounted on a PCB.
It is a further object of this invention to provide a device of the above type wherein a compliant mask or blanket is utilized to support the PCB and/or to provide molten solder to selected portions of the PCB to effect installation or replacement of components or devices on the board.
It is a further object of this invention to provide a compliant mask for use in a device of the above type where holes in the mask may either be pre-cut to conform to the size of standardized electronic devices or may be cut by the operator at the time the component or components are to be removed and/or installed.
It is a further object of the invention to provide an improved apparatus of the above type wherein molten solder or the like is used to remove or install the components.
It is a further object of this invention to provide an improved apparatus of the above type wherein a component to be installed or removed may be readily positioned with respect to the area where molten solder is applied to the board.
It is a further object of this invention to provide an improved apparatus of the above type where the level of the molten solder with respect to the PCB may be subject to both coarse and fine adjustment.
It is a further object of this invention to provide in an apparatus of the above type means for detecting when the molten solder has reached a predetermined level with respect to the PCB.
It is a further object of this invention to provide in a device of the above type means for positively holding the PCB in place while a component is being either removed or installed with respect thereto.
It is a further object of this invention to provide means for removing dross from the molten solder in a open-loop type of soldering apparatus.
In general, the objects of this invention further include provision of improved apparatus for (1) rapid, simultaneous lead soldering or desoldering, (2) component isolation, (3) PCB stress prevention, (4) controlled temperature, and (5) through-hole cleaning capability.